Question

What happen to the atomic number of an element, when it emits a $\beta -$particle ?

Answer 1

1. A radioactive element emits $\beta -$particles, its mass number remains the same but the atomic number increases by one unit.
2. Because $\beta -$particles have mass number zero but negatively charged particles.

${}_Z{}^{A}X\to {}_{z+1}{}^{A}Y+{}_{-1}{}^{0}e$

Hence, a radioactive element emits $\beta -$particles its atomic number increases by one unit.